Usually, a one-way clutch integrated with a rolling bearing has a structure in which a sprag one-way clutch is disposed on one or both axial sides of a rolling bearing such as a rolling bearing, and the inner and outer races of the rolling bearing are integrated with those of the one-way clutch, respectively.
In such a one-way clutch integrated with a rolling bearing, in order to facilitate assembling and enhance compactness, various countermeasures are taken mainly on a cage.
FIG. 14 is a partially cutaway front view of an example of a conventional one-way clutch integrated with a rolling bearing in which a sprag one-way clutch is disposed on both axial sides of a ball bearing, FIG. 15 is an axial section view of the example, and FIG. 16 is an exploded perspective view of a cage and a spring and side plate.
In this example, ball bearing raceway surfaces 61a and 62a are formed in axial center portions of an inner race 61 and an outer race 62, respectively. One-way clutch raceway surfaces 61b and 61c, and 62b and 62c are formed on both sides of the ball bearing raceway surfaces. A plurality of balls 63 serving as rolling members are rollably arranged between the ball bearing raceway surfaces. A plurality of sprags 64 are arranged between the one-way clutch raceway surfaces which are on both sides of the ball bearing raceway surfaces. The balls 63 and the sprags 64 are held at predetermined intervals in the circumferential direction by a common cage 65 which is configured by engaging and integrating two annular members 651 and 652 with each other in the axial direction. Spring and side plates 66 in each of which plural spring pieces 66a for respectively urging the sprags 64 in a locking direction are formed on the outsides of the sprags 64 are fixed to the annular members 651 and 652 constituting the cage 65, respectively.
In the two annular members 651 and 652 constituting the cage 65, recesses 651a and 652a which, under a state where the members are engaged with each other, configure pockets for housing the balls 63 in the center portion are formed in one axial end side and at constant intervals in the circumferential direction, and pockets 651b and 652b for housing the sprags are formed in the opposite end side. In one of the two annular members 651 and 652, or the annular member 651, a claw 651c which elongates in the axial direction is formed in plural positions along the circumferential direction. In the other annular member 652, plural recesses 652c with which the claws 651c are to be fittingly engaged are formed.
The thus configured one-way clutch integrated with a rolling bearing is assembled in the following manner. A required number of balls 63 are inserted and arranged between the inner race 61 and the outer race 62 and at approximately constant intervals in the circumferential direction. Thereafter, the annular members 651 and 652 are inserted between the inner race 61 and the outer race 62 so as to sandwich the balls 63 from the both sides in the axial direction. The claws 651c are respectively inserted into the recesses 652c so as to be engaged therewith, whereby these members are integrated with each other. An undercut is disposed in each of the claws 651c and the recesses 652c. As shown in FIG. 17 which is an enlarged axial section view showing an engagement state, an inclined face 651d is formed in the tip end side of each of the claws 651c, and an engaging portion 651e is formed in the basal end. An engaging portion 652d which is to be engaged with the engaging portion 651e is formed in each of the recesses 652c. Because of the engaging portions 651e and 652d, in an assembling process, the annular members 651 and 652 can be easily engaged with each other by snap fit, and, after assembling, the engagement state is prevented by the engagement of the engaging portions 651e and 652d from being easily cancelled (for example, Japanese Patent Publication (Kokai) No. 2000-304068 (pages 2 to 4, and FIGS. 2, 3, and 7)).
As a structure in which a sprag one-way clutch is disposed on one side of a rolling bearing, also a configuration is known in which a cage for a rolling bearing is axially integrated with that for a sprag in the axial direction via an engagement mechanism (for example, see Japanese Patent Publication (Kokai) No. HEI11-72127 (pages 3 and 4, and FIGS. 4 to 9)).
Usually, a one-way clutch integrated with a rolling bearing which is configured by integrating a rolling bearing such as a ball bearing with a sprag one-way clutch is structured in the following manner. As exemplarily shown in an axial section view of FIG. 18, rolling bearing raceway surfaces 41a and 42a are formed on an inner race 41 and an outer race 42, respectively, and plural rolling members 43 are rollably arranged between the raceway surfaces. In the inner race 41 and the outer race 42, one-way clutch raceway surfaces 41b and 42b are formed in parallel with the rolling bearing raceway surfaces 41a and 42a, respectively. A plurality of sprags 44 are arranged between the one-way clutch raceway surfaces. The rolling members 43 and the sprags 44 are arranged by a common cage 45 at constant pitches in the circumferential direction in an annular space formed between the inner race 41 and the outer race 42. Each of the sprags 44 is urged in a locking direction by urging means such as a garter spring 46.
As shown in the figure, usually, the sprag raceway surfaces 41b and 42b of the inner race 41 and the outer race 42 are usually formed as extended faces of shoulder portions 41c and 42c of the rolling bearing raceway surfaces 41a and 42a, or so as to have the same diameters as those of the shoulder portions 41c and 42c. 
In a sprag one-way clutch, as the J space which is the distance between the raceway surfaces of inner and outer races is larger, the size of useful sprags can be made larger so that the performance including the transmission torque can be improved. In the conventional one-way clutch integrated with a rolling bearing shown in FIG. 18, the diameters of the sprag raceway surfaces of the inner and outer races are respectively equal to those of the shoulder portions of the rolling bearing raceway surfaces, and hence the size of the J space is approximately constant in accordance with the model number (size) of the rolling bearing to be integrated. Therefore, improvement of the performance of a one-way clutch is limited.
In order to widen the J space as compared with a conventional one-way clutch integrated with a rolling bearing to improve the performance including the transmission torque, the inventors proposed a one-way clutch integrated with a rolling bearing in which, as shown in an axial section view of FIG. 19, a step 510 is formed between a shoulder portion 51c adjacent to a rolling bearing raceway surface 51a and a one-way clutch raceway surface 51b, for one of an inner race 51 and an outer race 52 (in FIG. 19, the inner race 51), whereby a larger J space can be ensured (see Japanese Patent Publication (Kokai) No. 2000-291651). FIG. 19 exemplarily shows a one-way clutch integrated with a rolling bearing of the type in which rolling elements (balls) 53 of the rolling bearing, and sprags 54 of the one-way clutch are held by dedicated cages 55 and 56, and a spring member 57 wherein a plurality of spring pieces 57b are formed integrally on an annular base member 57a is used so that the sprags 54 are urged in the locking direction by the spring pieces 57b (Japanese Patent Publication (Kokai) No. 2000-291651 (pages 2 to 4, and FIG. 1).
In the proposed one-way clutch, the race in which the step is formed is determined so as to be that on the side of one of fitting counterparts S and H which has higher shape accuracy of the fitting surface, whereby accuracy of the race in which the thickness of the portion where the one-way clutch raceway surface is formed is reduced by the formation of the step can be prevented from being lowered in accordance with the counterpart as a result of the fitting.
Usually, a one-way clutch integrated with a rolling bearing which is configured by integrating a rolling bearing such as a rolling bearing with a sprag one-way clutch has the following structure. As exemplarily shown in FIG. 14 which is a partially cutaway front view, and FIG. 15 which is a section view taken along the line A-A in FIG. 14, the rolling bearing raceway surfaces 61a and 62a are formed on the inner race 61 and the outer race 62, respectively, and the rolling members 63 are rollably arranged between the rolling bearing raceway surfaces. In the inner race 61 and the outer race 62, the one-way clutch raceway surfaces 61b and 62b, and 61c and 62c are formed in parallel with the rolling bearing raceway surfaces 61a and 62a, and the sprags 64 are arranged between the one-way clutch raceway surfaces.
The rolling members 63 and the sprags 64 are held in an annular space formed between the inner race 61 and the outer race 62, at constant pitches in the circumferential direction by the cage 65 which is commonly used in this example. In this example, the cage 65 has a structure in which the two annular members 651 and 652 are integrated with each other in the axial direction, and comprises pockets for the rolling members 63 and those for the sprags 64. The rolling members 63 and the sprags 64 are housed in the pockets so as to be arranged at constant pitches in the circumferential direction. The sprags 64 are urged in the locking direction by the spring and side plates 66 in each of which plural spring pieces 66a are formed on the annular base member 66b (for example, Japanese Patent Publication (Kokai) No. 2000-304068 (pages 2 to 4)).
In such a one-way clutch integrated with a rolling bearing, lubrication is conducted by grease, and hence the space between the inner and outer races is filled with grease. In the a one-way clutch integrated with a rolling bearing disclosed in Japanese Patent Publication (Kokai) No. 2000-304068, therefore, the spring and side plates 66 which are disposed in the axis end portions exert a function of preventing grease from leaking.
Since the two annular members 651 and 652 constituting the cage 65 have the claws 651c or the recesses 652c each having an undercut, holes for enabling molds to be extracted are required. In the annular members 651 and 652, therefore, it is necessary to form axial through holes which are indicated by H in the first annular member 651 of FIG. 16 (with respect to the second annular member 652, the through holes are not shown in the figure, and are formed in positions where the recesses 652c are to communicate with the sprag pockets 652b). The spring and side plates 66 prevent the grease from leaking through the holes.
The mold extracting holes are used also as holes for filling the grease between the inner race 61 and the outer race 62. After one of the spring and side plates 66 is attached and before the other spring and side plate 66 is attached, the grease is filled via the axial through holes on the side where the spring and side plate 66 is not attached. Thereafter, the other spring and side plate 66 is attached. As a result, the workability of the assembly process including the grease filling work can be improved.
In order to reduce the production cost, the structure in which a one-way clutch is disposed on one side of a rolling bearing is more advantageous than that in which a one-way clutch is disposed on both sides of a rolling bearing. In the case where the above-described technique of Japanese Patent Publication (Kokai) No. 2000-304068 in which two annular members are axially engaged with each other by an engagement mechanism including an undercut is applied to a structure in which a one-way clutch is disposed only on one side, a spring and side plate is attached only to the one side where the one-way clutch is disposed. Therefore, grease on the other side must be sealed by additionally disposing a dedicated side plate or the like.
It is an object of the invention to provide a one-way clutch integrated with a rolling bearing which has a structure where a one-way clutch is disposed on one side of a rolling bearing, and in which a side plate or the like for preventing grease from leaking is not required on the side where the one-way clutch is not disposed, the workability of the assembling process including a grease filling work is excellent, and the grease can be satisfactorily distributed over the raceway surfaces of inner and outer races.
As a result of the proposal in Japanese Patent Publication (Kokai) No. 2000-291651, the J space can be widened as compared with a conventional one-way clutch integrated with a rolling bearing of the same kind. The race in which the step is formed can be determined so as to be that on the side of one of fitting counterparts which has higher shape accuracy of the fitting surface, so that reduction of the accuracy of the one-way clutch raceway surface due to a reduced thickness can be prevented from occurring during fitting. However, reduction of the thickness is naturally limited. This causes a bottleneck in a countermeasure in which the J space is widened to increase the size of sprags.
It is an object of the invention to provide a one-way clutch integrated with a rolling bearing in which the J space can be further widened as compared with the above-mentioned proposal, so that larger sprags can be used, and which is therefore small in size and produces a larger transmission torque.
As a result of the proposal, the J space can be widened as compared with a conventional one-way clutch integrated with a rolling bearing of the same kind, and the performance including the transmission torque can be improved. In the case where the proposed technique is applied to a portion where the space between a shaft and a housing is small and a thin rolling bearing is used, however, the J space is limitedly ensured.
In a one-way clutch integrated with a rolling bearing, sprags in a locked state transmit a torque while being locked between inner and outer races. Therefore, the fitting of the inner race to the shaft, and that of the outer race to the housing must be tight at a degree which is higher than a certain level. If not, there arises the possibility that, in a locked state, a slip occurs between the inner race and the shaft or the outer race and the housing. Consequently, a large assembly load must be applied to both the shaft and the housing, and the workability of the assembling process is not excellent.
The invention has been conducted in view of such circumstances. It is an object of the invention to provide a one-way clutch integrated with a rolling bearing in which the J space can be widened as compared not only with a conventional one-way clutch integrated with a rolling bearing but also with a one-way clutch integrated with a rolling bearing according to the proposed technique, so that, even when applied to a portion where a thin rolling bearing is used, a J space of a sufficiently large size can be ensured and a large torque transmission ability can be exerted, and the workability of a process of incorporating to a shaft or a housing can be improved.
In a rolling bearing, when an adequate gap is not formed between the raceway surfaces of inner and outer races and the outer peripheral face of each rolling member, the rolling member does not roll in a desired manner, and hence the performance cannot be exerted. Particularly, a radial gap which is a gap in a radial direction after assembly is changed from that before assembly by deformation due to incorporation to a counterpart. Therefore, radial dimensions of the raceway surfaces of the inner and outer races are measured so that the gap in production, or the so-called initial gap has a value in which a value corresponding to deformation due to fitting fixation of the inner race or the outer race to a counterpart such as a rotation shaft or a bearing box is considered. A work which is called matching, and in which the size of rolling members to be incorporated is selected in accordance with the dimensions is conducted. Thereafter, the assembling process is conducted.
By contrast, a sprag one-way clutch cannot exert the ability unless the J space which is the radial dimension between the raceway surfaces of the inner and outer races for the one-way clutch is adequately held and the radial gap with respect to a sprag is optimumly held.
In a one-way clutch integrated with a rolling bearing in which a rolling bearing is integrated with a one-way clutch, the inner race and the outer race are often incorporated into respective counterparts by an interference fit. Therefore, the inner race is deformed in a direction along which the diameter expands, and the outer race is deformed in a direction along which the diameter contracts, whereby, in a state where they are incorporated into respective counterparts, the J space is correspondingly narrowed. The reduction degree of the J space is varied depending on the fitting to the counterpart and the dimensional accuracy of the counterpart.
In order to optimumly hold the J space after assembly, a conventional one-way clutch integrated with a rolling bearing is processed in the following manner. As shown in axial section views of FIGS. 20A and 20B respectively showing only the inner race 61 and the outer race 62, the diameters ICDi and OCDi of the one-way clutch raceway surfaces 61b and 62b of the inner race 61 and the outer race 62 are independently controlled irrespective of the diameters IBD and OBD of the rolling bearing raceway surfaces, and processed into plural dimensions ICDi (i=1, 2, 3, . . . ) and OCDi (i=1, 2, 3, . . . ) in accordance with the kinds of the counterparts to which the rolling bearing is to be incorporated, so that an initial J space corresponding to the kinds of the counterparts is obtained.
This causes the number of steps of inspecting and controlling the dimensions during a production process, and increases the production cost.
The invention has been conducted in view of such circumstances. It is an object of the invention to provide a method of producing a one-way clutch integrated with a rolling bearing in which the number of steps of inspection and control during a production process can be reduced as compared with a conventional art and hence the production cost can be lowered.